When essentails installed on server, and running command /time set 0 world time not resets to 0, just added 24000 ticks. After this vanilla method world.getWorldTime return really long value like world.getTotalWorld time. I writing mod under my client and have installed craftbukkit+forge build, after i find out this bug. After some debug i am sure, what problem in your plugin.

MC version: 1.12.2
CraftbukkitAPI version: 1.12.2-R0.1-SNAPSHOT
ess version output:

EssentialsX version: 2.17.1.0
PermissionsEx version: 1.23.4
EssentialsXSpawn version: 2.17.1.0
Vault is not installed. Chat and permissions may not work.
You are running unsupported plugins!

Can you explain more why this is a breaking feature? Vanilla also has a time command, which does much the same as Essentials. This sounds like it is much more likely a problem with your mod.

In minecraft we have method world.getWorldTime() applies to world variable. In vanilla/forge it is return long value [0-24000). When world time gets 24000 this variable automaticly resets to 0. But when essentials installed on server, this variable do not resets to 0 by command or just when worldtime is 24000. It is increasing unlimited. It is bug, because we have also method world.getTotalWorldTime() which return overall time of world. But somehow with essentials this two methods works same. I checked it on my server build with all mods & plugins installed, when removing essetials - bug disappears.

I do not know how, but essentials somehow changing behaviour of minecraft's method. Please check it.

This discrepancy lies with your server software. Bukkit and MCP/Forge expose different time-related methods to plugins and mods respectively, and your server software doesn't appear to implement the Bukkit methods in a way that works properly with MCP/Forge mods. Please report this to the developer of your server software. EssentialsX does not and will not support hybrid servers.